[Eurocode drawing] add grid. add function to compute the percentage of significant trend on an example

[EXTREME ESTIMATOR] add test confidence interval. Add confidence interval with the ci method in the Bayesian case. add test for the stationary case. put the division by 100 (to get snow load) in eurocode vizualizer

[EXTREME ESTIMATOR] Add MLE extreme estimator. refactor test gev temporal extremes. move confidence interval results

[EUROCODE GRAPH] update burn in percentage to 0.5 (update test). delete test region eurocode. update eurocode graph.

[EUROCODE DATA] improve display for the eurocode return level graphs. rename linear margin temporal models.

[EUROCODE][DRAWING PER REGION] modify test region eurocode. add test_ gev temporal bayesian. add stationary version for the Bayesian. refactor utils at the root, to root_uils to avoid weird import issues.